Assessing EDR and a novel deer repellent for reducing by-kill of white-tailed deer (Odocoileus virginianus), during aerial 1080 operations

ABSTRACT

A 2014 carcass search survey confirmed that Tiakina Ngā Manu aerial 1080 operations, undertaken to protect resident mohua (Mohoua ochrocephala) from increases to predator populations following substantial beech (Nothofagus sp.) mast events, cause mortality for Wakatipu white-tailed deer. Non-target by-kill of deer generates significant public opposition to predator control operations. We assessed if a current deer repellent (EDR) and a repellent in development (Pestex-DR) were effective at repelling captive white-tailed deer from consumption of nontoxic baits, commonly used in Tiakina Ngā Manu operations. Both repellents were found to significantly decrease bait consumption, and we observed clear displays of aversion to repellent baits by captive deer. Ten GPS collared wild white-tailed deer were then monitored following a Tiakina Ngā Manu operation using EDR in 2016. One collared deer was poisoned following the operation, confirming that EDR is not 100% effective. We recommend the most effective available deer repellent be used for future Tiakina Ngā Manu operations over the Wakatipu white-tailed deer habitat to minimise public opposition to these predator control operations. In addition, our results suggest that differences in the boundary size and shape of operations may account for some of the variability in non-target by-kill observed between studies.

KEYWORDS:

• Sodium fluoroacetate
• valued introduced species
• recreational hunting
• New Zealand
• Otago

Acknowledgements

The authors thank the Department of Conservation for supplying both the non-toxic RS5 cereal bait without repellent and bait coated in Epro deer repellent for use in the captive trial, also for permissions to undertake research and flexibility when method alteration was required. The authors also thank Pest Control Research Ltd for supplying their RS5 cereal baits with incorporated double strength Pestex-DR repellent. Garry Ottmann from the Game Animal Council provided a collar and assistance in collaring the deer. Sir Richard Hayes and his net gun operator assisted in deer capture and relocation. Grant Morriss (Manaaki Whenua – Landcare Research) assisted in method development. Lastly, the authors gratefully acknowledge Mr Marcus Pinney for allowing me to conduct the captive trial on his white-tailed deer.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The following provided funding without which we could not have undertaken the wild deer monitoring: EPRO Ltd, Safari Club International (NZ Chapter) and the New Zealand Deerstalkers Association (NZDA), particularly Wellington and Marlborough Branches and various individual donations to the ‘Givealittle’ page.